Fraternitè

Algebra Level pending

On July 14, 1789, all brothers in a family calculated the sum of their ages X X and then the sum Y Y of their years of birth. It turned out that X + Y = 17881 X + Y = 17881 . How many of them were born in March at most?


The answer is 1.

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1 solution

Claudia Manotti
Aug 13, 2017

a is referred to the number of brothers born by 14 July and b the number of those born after. It is 17881 = a 1789 + b 1788 = ( a + b ) 1788 + a 17881 = a1789 + b1788 = (a + b) 1788 + a . Since 17881 < 178 8 2 17881 <1788 ^ 2 we get ( a + b ) < 1788 (a + b) <1788 . So (a + b) is the quotient 10 of the division of 17881 for 1788 and b is the rest 1. Thus there is 10 brothers, of which 9 born after July 14 and at most one may be born in March.

Nice question, but the title Fraternité should end in é.

H K - 3 years, 10 months ago

Ok, probability right for me 50%

Claudia Manotti - 3 years, 10 months ago

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